Enhancement mode metal-oxide-semiconductor field effect transistor
View Patent ↗An implant-free enhancement mode metal-oxide semiconductor field effect transistor (EMOSFET) is provided. The EMOSFET has a III-V compound semiconductor substrate and an epitaxial layer structure overlying the III-V compound semiconductor substrate. The epitaxial material layer has a channel layer and at least one doped layer. A gate oxide layer overlies the epitaxial layer structure. The EMOSFET further includes a metal gate electrode overlying the gate oxide layer and source and drain ohmic contacts overlying the epitaxial layer structure.
1. An implant-free enhancement mode metal-oxide semiconductor field effect transistor (EMOSFET) comprising:
a III-V compound semiconductor substrate;
an epitaxial layer structure overlying said III-V compound semiconductor substrate, said epitaxial material layer comprising a channel layer and at least one doped layer;
a gate oxide layer overlying said epitaxial layer structure;
a metal gate electrode overlying said gate oxide layer; and
source and drain ohmic contacts overlying said epitaxial layer structure;
wherein said EMOSFET is without source and drain extension implants of the same dopant type as the at least one doped layer.
2. The implant-free EMOSFET of claim 1 , said at least one doped layer comprising a delta-doped layer.
3. The implant-free EMOSFET of claim 1 , said epitaxial layer structure comprising a spacer layer overlying said channel layer and underlying said gate oxide layer.
4. The implant-free EMOSFET of claim 3 , said spacer layer comprising aluminum gallium arsenide (AlGaAs).
5. The implant-free EMOSFET of claim 1 , said channel layer comprising indium gallium arsenide (InGaAs).
6. The implant-free EMOSFET of claim 1 , said III-V compound semiconductor substrate comprising gallium arsenide (GaAs).
7. The implant-free EMOSFET of claim 1 , said gate oxide comprising Ga 2 O 3 .
8. The implant-free EMOSFET of claim 1 , further comprising a field plate positioned at least partially within said gate oxide.
9. The implant-free EMOSFET of claim 1 , further comprising a field plate positioned overlying said gate oxide.
10. The implant-free EMOSFET of claim 1 , further comprising a low dose implantation region positioned within said epitaxial layer structure, said low dose implantation region of a conductivity type opposite to said at least one doped layer.
11. The implant-free EMOSFET of claim 1 , wherein said metal gate electrode is a metal step gate electrode.
12. An enhancement mode metal-oxide semiconductor field effect transistor (EMOSFET) comprising:
a III-V compound semiconductor substrate;
an epitaxial layer structure overlying said III-V compound semiconductor substrate, said epitaxial layer structure comprising a channel layer and at least one delta-doped layer;
a gate oxide layer overlying said epitaxial layer structure;
a metal gate electrode overlying said gate oxide layer, said metal gate electrode having a work function; and
source and drain ohmic contacts overlying said epitaxial layer structure;
wherein said metal gate electrode is selected to have said work function and said delta-doped layer is doped to a level so that enhancement mode operation is achieved.
13. The EMOSFET of claim 12 , said III-V compound semiconductor substrate comprising gallium arsenide (GaAs).